1. Field of the Invention
The present invention is directed to a carder for manufacturing non-woven fabrics from fibrous material which is provided with an air-guiding box to improve the uniformity and the non-woven structure of the fibrous material.
2. DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 4,523,350, the disclosure of which is hereby incorporated by reference, discloses a carder wherein the worker rollers following the licker-in roller are provided as a main roller comprising a subsequent matting roller and being preceded by at least one pair of worker rollers and clearer rollers. The worker and clearer rollers which generally have a smaller diameter than the main matting roller or rollers in the apparatus described thereby serve the purpose of managing an adequate carding of the fibrous material, whereas the matting roller or rollers achieve an optimum uniformity of the matted non-woven structure over the entire width of the non-woven material to be manufactured. The fabric which results has the generally desirable characteristic of having a ratio of longitudinal strength to transverse strength at about 1:1 over the entire extent of the non-woven fabric.
The carder described in the aforementioned patents has proven itself commercially. As a result of the increased tendency to increase the working width of the carders, however, it has been found that the use of the worker rollers and clearer rollers necessarily having a relatively small diameter in comparison to the main rollers involves greater and greater difficulties. For example, with a width of 4 meters or more, sags of the rollers are unavoidable. Further, the structural outlay is relatively great as a consequence of the numerous, different circumferential speeds of the rollers of different diameters such as the main rollers, matting rollers, as well as the worker, and clearer rollers.
The art discloses a carder where, unlike the carder mentioned above, the worker rollers following one another rotate in opposite directions and clearer rollers are provided which have a smaller diameter than the worker rollers. This system has the disadvantage that the individual worker rollers must exhibit an increased speed so that the carding effect obtainable for the number of possible worker rollers following one another is limited since it is difficult to achieve such increased speeds.
In order to improve the uniformity of the matted non-woven structure over the entire width of the fabric with reduced structural outlay and high working speeds, U.S. Pat. No. 4,723,343 proposes a carder wherein a satisfactory carding effect and uniformity of the non-woven fabric can be achieved over the full width wherein the fibrous material is conducted with adjustable, partial back-storing over at least three workers of identical diameter positioned in mutual, adjustable engagement with each other. Combined with the adjustability of the relative speeds as well as the relative positions of the individual worker rollers, a controllable back-storing is thus achieved at each individual worker roller, the surface structure being shaped in the form of saw tooth fittings or the like.
U.S. Pat. No. 4,723,343 discloses wherein a wedge shaped air-guiding box projects into the transfer region between the main roller and the matting roller, the air-guiding box being adjustable in height and transversely relative to the roller shell. The air-guiding box can be either pressurized or unpressurized but can not be charged with a vacuum for suctioning. It improves the strong air turbulences present in the area between the cooperating worker rollers in which the non-woven fabric is formed, so that an optimum and uniform non-woven formation is promoted.